1. Technical Field
The resent disclosure relates to controlling the amount of torque applied to a threaded connection. More particularly, the present disclosure relates to an apparatus for applying a controlled amount of torque to either install or remove a threaded connection working member.
2. Description of Related Art
Torque wrenches are well known devices which most commonly use one or more elastic bending rods as in U.S. Pat. No. 5,734,113 to Vogt et al. (xe2x80x9cVogt et al.xe2x80x9d) or an axial spring device as in U.S. Pat. No. 5,859,371 to Hsieh (xe2x80x9cHsiehxe2x80x9d) and U.S. Pat. No. 5,911,801 to Fravalo et al. (xe2x80x9cFravalo et al.xe2x80x9d) as the primary source of their torque sensing mechanism. These torque wrenches use complex mechanisms that frequently employ one or more helical springs, roller bearings, an rod devices enclosed within their handle cavity. For example, Fravalo teaches a wrench head that pivots inside a hollow cavity and interfaces with a plunger rod type device that employs at least one rolling body to minimize friction. This mechanism then interfaces with an axially coiled spring. These internal mechanisms are too complex to support disassembly for ease of sterilization and are too expensive to use as a disposable torque wrench device.
Some patents directly address some degree of dismantling or removing and replacing internal components such as U.S. Pat. No. 4,249,435 to Villeneuve et al. (xe2x80x9cVilleneuve et al.xe2x80x9d) and U.S. Pat. No. 5,734,113 to Vogt et al. (xe2x80x9cVogt et al.xe2x80x9d). These torque devices are also internally complex and cannot be cost effectively dismantled, sterilized, and then reassembled for use in sterile environment.
Another aspect of torque wrench technology involves a mechanism to preclude over torquing through a slip mechanism within the torque wrench. One torque wrench that has a leaf spring slip mechanism is U.S. Pat. No. 5,224,403 to Rueb (xe2x80x9cRuebxe2x80x9d). Rueb teaches two basic embodiments of cantilevered beam leaf spring type torque wrench mechanisms that slip when the torque limit is exceeded.
In the first embodiment, the leaf spring acts as a cantilever beam that extends from the handle to perpendicularly engage a single symmetrical vertical gear tooth in the wrench head. Torque values are adjusted on the handle by varying the effective length of the cantilevered beam. In a similar second embodiment, Rueb discloses two perpendicular springs located within the wrench head that engage gear teeth a with complex double tooth shape. The perpendicular springs that engage the complex double tooth gears are held in place by two retaining shoulders of different height that create a shorter stiffer beam with greater resistive force in the counterclockwise direction than in the clockwise direction. Each complex double tooth of the gear has a single tooth side, where only the long tooth is engaged, and a double tooth side, where first the short and then the long tooth is engaged. The single tooth and double tooth sides are symmetrically sloped. Maximum clockwise torque is achieved as the longer tooth is engaged on the single tooth side of the complex double tooth gear by the perpendicular leaf spring and the perpendicular leaf spring is forced past the resisting counter force of the spring retaining shoulder. The lower clockwise supporting spring retaining shoulder creates a cantilever beam with a longer, less resistive counter force.
This second embodiment removes a threaded member in the counterclockwise direction without adjustments using a combination of the double tooth form and the shock force imparted by the spring as it forced past the first shorter tooth and then impacts upon the second longer tooth. In addition, the longer counterclockwise retaining shoulder support provides a shorter cantilevered spring that provides greater resistive force than in the clockwise direction.
The second embodiment of Reub is distinctly limited by its lack of ability to adjust for different torque values and its internal complexity which precludes it from being disassembled, sterilized, and reassembled for use in a sterile environment. As a result, this and other current torque wrench designs require the surgical instrument to be removed from the sterile environment, their working member removed and replaced with the proper torque, and then the surgical instrument must be resterilized. Torque wrenches that have mechanisms such as those above and are used in medical applications are typically not used in a sterile environment.
Accordingly, there is a need for improved apparatus for applying a controlled amount of torque that can be sterilized using readily available sterilization equipment. It is desirable that the apparatus be simple in construction, easy to disassemble and reassemble, and that it does not require calibration upon reassembly. It is desirable to provide a torquing apparatus that is so inexpensive that it can be disposable. It is further desirable that the torquing apparatus have the potential to apply different torques for different threaded member applications and require no adjustments for the installation or removal of a specific threaded connection.
A torque apparatus is provided that employs a plurality of leaf spring elements engaging a plurality of asymmetrical drive teeth sides to establish a range of preset torque values for the installation and removal of threaded connecting devices. The preset torque values can be readily changed by employing different quantities of leaf springs, differing leaf spring designs, or varying the geometry of the rotor drive teeth. The leaf spring to rotor drive teeth interface provides a slip mechanism to prevent over-torquing when torque values for either the installation or removal of a threaded connecting type device are exceeded. The wrench head may be hermetically sealed in its preferred configuration, or in an alternative configuration capable of full disassembly. Both configurations can be readily sterilized using an autoclave or similar sterilization methods. The second configuration adds the advantage that the apparatus can be reconfigured for different torque applications without calibration within a sterilized environment. The wrench can also be employed as a disposable device.
The invention, together with attendant advantages, will be best understood through by the reference to the following detailed description of the invention when used in conjunction with the figures below.